As computer technology continues to advance, electronic components such as central processing units (CPUs) of computers are made to provide faster operational speeds and greater functional capabilities. When a CPU operates at a high speed in a computer enclosure, its temperature can increase greatly. It is desirable to dissipate the generated heat quickly, for example, by using a heat sink attached to the CPU in the enclosure. This allows the CPU and other high-performance electronic components in the enclosure to function within their normal operating temperature ranges, thereby assuring the CPU quality of data management, storage and transfer. Oftentimes, a retainer is required for mounting the heat sink to the CPU.
One conventional retainer developed to mount a heat sink to a CPU is illustrated in FIG. 5. The retainer comprises a retention module 97 and two clips 90. The retention module 97 comprises four locking feet 98 formed at four corners thereof. Each locking foot 98 defines a locking opening 99 therein. Each clip 90 comprises an elongate strap 93 and a cam-type lever 92 pivotally connected to a middle of the strap 93. Two opposite ends of the strap 93 integrally extend downwardly to form a pair of legs 94. A hook 95 is formed at a bottom portion of each leg 94 corresponding to a respective locking opening 99 of the retention module 97. The retention module 97 is fixed on a printed circuit board around a CPU (not shown), and a heat sink (not shown) is mounted on the CPU. In assembly, the clips 90 are placed on opposite sides of the heat sink. The straps 93 of the two clips 90 are downwardly pressed to cause the hooks 95 to interlock with the corresponding legs 94 at the locking openings 99. However, the clip 90 is integral formed and therefore has a large rigidity. As a result, large force is needed in operation. Furthermore, the legs 94 of the clips 90 are prone to slide over the feet 98 to damage the CPU when the large force is applied.